Michael ibvoesky pupin



Jan 31, 1928. 7 1,657,587

M. a. PUFEN ELECTRICAL PULSE GENERATOR Filed Aug. '7, 1924 Michael ldvorskyPupin,

Patented Jan. 31, 1928.

UNITED srares Application filed August It, will.

This invention relates to a means of gen erating electrical pulses by eliciting the field of a dynamo electrical machine impulsively. This is accomplished by connecting the magnetizing field coilsot the generator in the plate circuits of thermionic tubes, the thermionic currentsol which are started and stopped by charging their grids to a higher orlower potential withrespect to the liloments,

The object of this invention is to produce impulsively electromotive forces and currents tor signaling, such as are required on ocean cables and long land lines, by in 'ng and breaking contacts between which the current flowis excessively small and sparking is thereby avoided. l

- r further object is to provide system by which the impulses may be applied at rapidly succeeding time "intervals without ences sive sparking at contact points. A further objectvis to provide a system by which, both positive and negative impulses can be applied in rapid succession without changingthe resistance between the ground and conductor over which the impulses are transmitted, as, is the case in the usual cable and telegraph practice, especially when the ground connection is through a co1nparatively low and constant impedance.

A further object is to provide a system which can be actuated from such mechanism as is usually employed in telegraphy for sending by impressing positive and negative pulses upon a telegraph transmission con: ductor, as by telegraph keys, or pertorateo tapes, or through sensitive relays from received telegraphic signals, which are then re peated and greatly amplified by the power of a dynamo-electric pulse generator,

In the accompanying sheet oi? drawings which forms a part of this description, the figure isa diagrammatic representation of the instrumentalities associated in this invention.

Referring to the figure, provision is made to transmit pulses both positive and negative from aLdircct-current pulse generator 10 to lines 11, 12'. The pulse generator is preterably provided with two sets of field coils l3, 14 on a suitably laminated steel. core, these being connected so that when one set is energized, current of one polarity will be generated, and when the other setis energised, current of the other polarity will be genersteel; Current for energizing these field lllerial it" o. 7%,774.

coils supplied "from a winding 15 or a douhle-woimd held-current generator, which m r r example, five hundred volts. .rhe on. 1: r tor the held 13 18 from the positlVO brush through a resistance 16, to the plate ll oi? a thermionic tube, thence when not opposed, through the grid 18 to the filan eut 19 ot the tube, thence to the middle pointot a transformer winding 20 which supplies the lilament heating current, and item this middle point to the grounded negative brush oi the winding. Flow through this circuit arrested in the tube when the grid is charged negatively to a sui l'icientl; high degree. For-this purpose asecond winding 21 is provided on the fieldcurrent generator, which generates for example, three hundred volts. This winding has its negativebrush connected to ground through ahigh resistance 22 and its positive: brush is connected through a suitable rcsistance 992- to the grounded negative brush oi the other winding. lita suitable adjustable point of resistance 22 a connection is made through a high resistance 23 to a bacl: contact 24-, which through a spring 25 gives to thegrid 18 and a condenser 26 a suitable potential which is negative with respect to the filament ill, to the point of symmetry of which the positive brush is connected through the adjustable resistance 22 and the middle point or the transformer winding 20. From the positive brush, a connection is made with an under contact 27 through a high resistance which gives to this contact a suitably high positive potential.

l t now the spring 25 is pressed down, thereby breaking contact with its back con tact 2st and making contact with its under contact 2'3", the grid will he cut oil from the source of negative potential by which it was ch ged negatively and through the under ct will be connected through the high resistance 28 with the positive brush of the winding by which it will be charged posilivel with respect to the filament. Current can them flow between the plate 17 and the filament 19, and through the winding 13 of the pulse generator, which will now he magnetized and a certain electromotive force will be developed in. the armature of the pulse generator 'lfhrcugh a iilar set or connections, current for cue u ing in a contrary direction the other set oilield coils i l oi the pulse generator trom the winding oi. the fieldfi I) current generator is supplied through a circuit which leads from the positive brush through a resistance 29 to the plate 30 of a second thermionic tube, thence when not opposed, through the grid 31 to the filament 32 of the tube, thence to the middle point of the transformer winding 20, and from this middle point to the grounded negative brush of the winding.- Flow through this circuit is arrested in. the tube when the grid 31 is negatively charged -from the second winding 21 of the field-current generator,

. whichhas itsnegative brush normally conpoint of the transformer winding 20. From the'positive brush connection is made with an under contact 37 through the high resistance28 which gives this contact a suitably high positive potential.

It now while the first spring 25 is in contact with its back contact 24, the second spring'35 is pressed down, thereby breaking contact with its back contact 3d and making contact with its under contact 37 the grid 31' will be cut off from the source of negative potential by which it was charged and through its under contact will be connectedthrough the high resistance 28 with the positive brush of the winding and will '1 be charged positively. Current can then flow between the plate 30 and the filament 32 and through the winding 14 of the pulse generator, which will now be magnetized oppositely from the magnetism which'was producedby the first field and an electromotive force of opposite polarity will be developed in the armature of the pulse generator. I I 7 'It is not intended that both springs shall 7 ever be actuated at the same time, and to indicatethat this is not to happen, keys 38, 39 for the operation of the contact springs are shown at opposite ends of an intermediately fulcrumed lever 40. In practice the contact springs are'actuated by any suit-- able mechanism such as is usually employed in telegraphy for impressing positive and negative impulses upon a telegraphic transmission conductor.

For .ordinary telegraphy it is necessary that the pulse generator fieldshould reach its full value in abouta one-hundred and twenty-fifth part ot-a second. The field core as well asthe armature core of the pulse gen 7 erator must therefore be sufliciently laminate'd. For the rapidities of makes and breaks which occur in ordinary ,telegraphy particularly over long submarine cables. fourteen mills sheet steel aliords a suificiently good lamination. Also the magnetizing current must attain its full value in a sufiiciently short time. For example, assume that the internal resistance R in each of the plate circuits of the thermionic tubes together with the external resistances 16 or 29 is five thousand ohms, and the inductance L of the field coil of the pulse generator is ten henrys, then the growth of the current C is given by the following formula.

in which E is the electromotive force in the plate circuit and 7s Since R divided by L is live hundred, it is obvious that when the time 25 is a one-hundred and twenty-fifth part of a second, the current C will have attained practically its full value.

By diminishing the number of turns in the magnetizing coils, which diminishes L, andby increasing R, the rapidity of the establishment of the full value of the magnetizing current and of the magnetic flux canbe increased to any reasonable amount, and the value of the resulting flow can be made to reach a desirable limit by increasing suitably the value of E. This can be done by a proper design of the thermionic tubes. The lowest value of the internal resistance of the tube is taken, which is the value when the grid is positively charged. But since the internal resistance of the tube increases when the thermionic current is diminished bythe increase oi the negative potential on the grid, it is obvious that the field of the pulse generator will lose or gain its magnetic flux at a rate which also depends upon the rate at which the grid is charged. This time interval can be regulated by the resistances 28, 23 and 33 in the grid circuits. Let these resistances be each equal to one hundred thousand ohms, and let the capacity of each grid and its associated condenser be equal to twenty-five milli-mierofarads, then the constant will be means tor varying the impedance in the grid circuit of one of the tubes to vary the excitation of one of the windings to produce impulses 01' one polarity in the line, and means for varying the impedance in the grid circuit of the other tube to produce impulses of the other polarity in the line, the

impedance of the plate circuits and of the conductors connecting the grids tothe charging sources being so adjusted that the magnetic flux produced by one Winding when the current in the other Winding is interrupted Will have a time constant which is determined Toy the inductance and the ohmic resistance of the'winding.

Signed at New York, N. Y, this sixth day of August, 1924.

MICHAEL IDVORSKY PUPIN. 

